In a conventional reference voltage generating circuit that includes a reference voltage generator configured to generate a reference voltage, a charge supply circuit, and a timer circuit, the charge supply circuit is controlled by the timer circuit so that an output (a power supply voltage, for example) from the charge supply circuit is supplied to a reference voltage output terminal of the reference voltage generator for a prescribed time, starting from a point in time at which the reference voltage generator was activated (see Japanese Laid-open Patent Publication No. 10-222234, for example). A capacitor is connected to the reference voltage output terminal of the reference voltage generator to stabilize its output.
In the conventional reference voltage generating circuit, however, a time during which the timer circuit performs counting is preset. If, for example, a power supply voltage is slowly raised, therefore, the counting time preset in the timer circuit may be too short for the output electric potential of the reference voltage generator to rise sufficiently. This may cause slow start-up operation. If a capacitor for smoothing the output voltage of the reference voltage generator is reduced to achieve fast start-up operation, variations in the power supply voltage and noise influence may become significant.
Accordingly, the conventional reference voltage generating circuit may not be capable of achieving both a high power supply rejection ratio (PSRR) and quick start-up operation.